A new fluorescence assay of trimethoprim and metabolites using quantitative thin-layer chromatography

Spectrophotometric determination of diaminopyrimidines using benzoquinone

The diaminopyrimidine derivatives trimethoprim (TMP), pyrimethamine (PMA) and 2,4-diaminopyrimidine (2,4-DAP) are found to react readily and efficiently in an aqueous solution with p-benzoquinone (p-BQ) to form a colored product with an absorption optimum wavelength of about 500 nm. The optimum reaction time, pH, temperature, solvent, and [p-BQ] are determined by separate trials. These conditions are confirmed by a MultiSimplex optimization method. The molar absorptivities of the TMP, PMA, and 2,4-DAP reaction products at 500 nm are 10,830, 10,650, and 9660 l mol(-1) cm(-1), respectively. TMP shows a linear range between 5 and 100 mg/l while PMA and 2,4-DAP exhibit linearity between 15 and 75 mg l(-1) and 5 and 30 mg l(-1), respectively. There is some specificity to this reaction; 2-aminopyrimidine does not react. Under the optimum conditions, sulfamethoxazole (SM) reacts rather poorly with a molar absorptivity of about 110 l mol(-) cm(-1). Using p-BQ, TMP in a pharmaceutical sample can be determined in the presence of SM using derivative spectrophotometry. The TMP-p-BQ reaction is adaptable for flow injection analysis.

Determination of isomeric N-oxide metabolites of some substituted 2,4-diaminopyrimidines by reversed-phase ion-pair high-performance liquid chromatography

Reversed-phase ion-pair high-performance liquid chromatography has been investigated for the separation, detection, identification and quantitation of the isomeric 1N- and 3N-oxide metabolites of metoprine, pyrimethamine and trimethoprim. A rapid and sensitive analytical method for the simultaneous determination of the isomeric 1N- and 3N-oxides of metoprine and pyrimethamine was devised for in vitro metabolic studies by optimisation of mobile phase pH, pairing-ion concentration, secondary-ion concentration and percentage organic modifier.

A prospective, randomized, double-blind study of trimethoprim-sulfamethoxazole for prophylaxis of infection in renal transplantation: clinical efficacy, absorption of trimethoprim-sulfamethoxazole, effects on the microflora, and the cost-benefit of prophylaxis

PURPOSE

To determine the efficacy of long-term prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMZ) for prevention of bacterial infection following renal transplantation, the absorption of TMP-SMZ in transplant patients, the effects of prophylaxis on the microflora, and the cost-benefit of prophylaxis.

PATIENTS AND METHODS

One hundred thirty-two adult patients selected to undergo renal transplantation participated in a randomized, double-blind, placebo-controlled trial.

RESULTS

Patients randomized to receive TMP-SMZ experienced fewer hospital days with fever (3.3% versus 7.7%, p less than 0.001) and significantly fewer bacterial infections during the transplant hospitalization after removal of a urethral catheter (0.76 versus 1.88 per 100 days, p less than 0.005) and following discharge from the hospital (0.08 versus 0.30 per 100 days, p less than 0.001). During the transplant hospitalization, a daily dose of 320/1,600 mg was highly effective for prophylaxis whereas 160/800 mg daily gave unexpectedly low blood levels and was effective only for prevention of urinary tract infections after catheter removal. Prophylaxis was most effective in prevention of infections of the urinary tract (24 versus 54, p less than 0.005) and bloodstream (one versus nine, p less than 0.01) and infections caused by enteric gram-negative bacilli (four versus 46, p less than 0.001), enterococci (six versus 22, p = 0.006), or Staphylococcus aureus (one versus nine, p = 0.01). Prophylaxis did not prevent urinary tract infection associated with urethral catheters in the early posttransplant period, but after catheter removal, reduced the risk of urinary tract infection threefold (p less than 0.001). No significant differences in colonization by TMP-SMZ-resistant gram-negative bacilli were identified between the two groups; patients given TMP-SMZ were, paradoxically, less likely to become colonized by candida, probably because of less exposure to antibiotics for treatment of infection. Recipients of prophylaxis did not have a higher rate of infection caused by TMP-SMZ-resistant bacteria or Candida; however, their infections were more likely to be caused by resistant bacteria than infections in patients in the placebo group (62% versus 18%, p less than 0.001).

CONCLUSIONS

Prophylaxis with TMP-SMZ, which is well tolerated, significantly reduces the incidence of bacterial infection following renal transplantation, especially infection of the urinary tract and bloodstream, can provide protection against Pneumocystis carinii pneumonia, and is cost-beneficial. Subnormal absorption of TMP-SMZ in the early posttransplant period mandates 320/1,600 mg daily for optimal benefit. Prophylaxis has little discernible effect on the microflora.

Determination of sulfadimethoxine, sulfamethoxazole, trimethoprim and their main metabolites in porcine plasma by column switching HPLC

A HPLC method for the determination of sulfadimethoxine, sulfamethoxazole, trimethoprim and their main metabolites in porcine plasma is reported. The metabolites under investigation were the N4-acetyl sulfonamides and 3'- and 4'-demethyl trimethoprim. In order to obtain a sensitivity of 25-50 ng ml-1, the application of column switching HPLC was investigated. An on-line preconcentration of the drugs and metabolites was preceded by an off-line sample pre-treatment. Parent compounds and metabolites were separated by reversed-phase HPLC followed by UV-detection. The mean recoveries for 4'-demethyl trimethoprim were greater than 80% while the mean recoveries for the other compounds were greater than 90%. Application of the method for analysis of plasma samples obtained from pharmacokinetic studies is described.

Determination of trimethoprim in pediatric samples by high-performance liquid chromatography

We describe and evaluate modifications to a known high-performance liquid chromatography assay of trimethoprim. The sensitivity, specificity and wide range of linearity (0.11-690 mumol/l) of this method make it suitable for analysing samples with large variations in volume and concentration. We have used it to study the pharmacokinetics of trimethoprim in children, including newborns. Automated injection is a useful option if the sample volume is not limited. The recovery (at 3.44 mumol/l) of the method was 99.8% with a coefficient of variation of 6.8% for manually injected samples. The corresponding results for automated injection were 97.9% and 12.8%.

Determination of trimethoprim metabolites including conjugates in urine using high-performance liquid chromatography with combined ultraviolet and electrochemical detection

A high-performance liquid chromatographic method for the determination of trimethoprim metabolites in pig urine was developed. The metabolites-glucuronic acid and sulphuric acid conjugates of phenolic metabolites formed by demethylation of trimethoprim-were quantitated after treatment of urine with beta-glucuronidase (Escherichia coli). The sulphuric acid conjugate was not susceptible to enzymatic hydrolysis and was therefore assayed as the conjugate by use of ion-pair chromatography on the reversed-phase column. In order to find suitable conditions for enzymatic hydrolysis of the glucuronides, the conjugates were obtained by gel chromatography of urine from a [14C] trimethoprim-treated pig.

Quantitative high-pressure liquid chromatographic procedure for the determination of plasma and tissue levels of 2,4-diamino-5-(3,4-dichlorophenyl)-6-methylpyrimidine (metoprine) and its application to the measurement of brain capillary permeability coefficients

A high-pressure liquid chromatographic assay for metoprine levels in aqueous media, serum, and tissue extracts has been developed that can measure concentrations of the drug in the 25-100 ng range with accuracy, reproducibility, and ease. The half-time for metoprine disappearance from rat plasma and capillary permeability coefficients for metroprine in rate brain tissue determined with this method are in excellent agreement with values determined for related drugs using labeled compounds.

NMR determination of trimethoprim and sulfamethoxazole in tablets and powders

An NMR spectroscopic method for the determination of mixtures of trimethoprim and sulfamethoxazole is described. Spectra are determined in dimethylsulfoxide-d6, containing 1,4-dinitrobenzene as an internal standard. Both synthetic mixtures and commercial formulations were assayed, and the results were compared to those obtained using the BP procedure.